Rheumatoid arthritis (RA) is a clinically important, chronic systemic autoimmune inflammatory disease affecting between 1.3 and 2.1 million persons in the United States (See, e.g., Alamanosa and Drosos, Autoimmun. Rev., 4:130-136 (2005)). RA is an autoimmune disorder of unknown etiology. Most RA patients suffer a chronic course of disease that, even with currently available therapies, may result in progressive joint destruction, deformity, disability and even premature death. More than 9 million physician visits and more than 250,000 hospitalizations per year result from RA.
Diagnosis of RA typically relies on clinical and laboratory evaluation of a patient's signs and symptoms. Generally, laboratory evaluation of a patient suspected of having RA may include determination of the level of certain antibodies in serum known as rheumatoid factor (RF) and antibodies to cyclic citrullinated peptide (anti-CCP). (See, e.g., Schellekens et al., Arthritis Rheum., 43:155-163 (2000); DiFranco et al., Rev. Rheum. Engl. Ed., 66(5):251-255 (1999); Rantapaa-Dahlqvist et al., Arthritis Rheum., 48:2741-2749 (2003); Li et al., Bioinformatics 22(12):1503-1507 (2006); Russell et al., J. Rheumatol., 33(7):1240-1242 (2006); Ota, Rinsho byori. Jap. J. Clin. Pathol., 54(8)861-868 (2006); Avouac et al., Ann. Rheum. Dis., 65(7):845-851 (2006)). While these antibodies are often found in the serum of RA patients, not all RA patients have them. An additional blood test known as the erythrocyte sedimentation rate (ESR) may also be used. An elevated ESR indicates the general presence of an inflammatory process, although not necessarily RA. Further blood tests may be used to assess the level of other factors, such as C-reactive protein (CRP) that have been associated with RA. In addition, radiographic analysis of affected joints may be performed. In sum, such currently available laboratory tests to diagnose RA are imprecise and imperfect.
In certain instances, diagnosis of RA is made if a patient satisfies certain American College of Rheumatology (ACR) criteria. Certain such criteria include morning stiffness in and around the joints lasting for at least 1 hour before maximal improvement; arthritis of three or more joint areas: at least three joint areas have simultaneously had soft tissue swelling or fluid (not bony overgrowth alone) observed by a physician; the 14 possible joint areas (right and left) are proximal interphalangeal (PIP), metacarpophalangeal (MCP), wrist, elbow, knee, ankle, and metatarsophalangeal (MTP) joints; arthritis of hand joints: at least one joint area swollen as above in wrist, MCP, or PIP joint; symmetric arthritis: simultaneous involvement of the same joint areas (as in arthritis of three or more joint areas, above) on both sides of the body (bilateral involvement of PIP, MCP, or MTP joints is acceptable without absolute symmetry); rheumatoid nodules: subcutaneous nodules over bony prominences or extensor surfaces or in juxta-articular regions that are observed by a physician; serum rheumatoid factor: demonstration of abnormal amounts of serum rheumatoid factor by any method that has been positive in fewer than five percent of normal control patients; radiographic changes: radiographic changes typical of rheumatoid arthritis on posteroanterior hand and wrist X-rays, which must include erosions or unequivocal bony decalcification localized to or most marked adjacent to the involved joints (osteoarthritis changes alone do not qualify). Diagnosis of RA is typically made if a patient satisfies at least four of the above criteria.
A number of published studies report the attempted identification of reliable biomarkers for diagnostic and prognostic purposes. (See e.g., Rioja et al., Arthritis and Rheum. 58(8):2257-2267 (2008); Pyrpasopoulou et al., Mol. Diagn. Ther. 14(1):43-48 (2010); US 2004/0009479; US 2007/0105133; WO 2007/038501; WO 2007/135568; WO 2008/104608; WO 2008/056198; WO 2008/132176; and WO 2008/154423). No clinically validated diagnostic markers, however, e.g., biomarkers, have been identified that enable clinicians or others to accurately define pathophysiological aspects of rheumatoid arthritis, clinical activity, response to therapy, prognosis, or risk of developing the disease. Accordingly, as RA patients seek treatment, there is considerable trial and error involved in the search for therapeutic agent(s) effective for a particular patient. Such trial and error often involves considerable risk and discomfort the patient in order to find the most effective therapy. Thus, there is a need for more effective means for determining which patients will respond to which treatment and for incorporating such determinations into more effective treatment regimens for RA patients.
It would therefore be highly advantageous to have additional diagnostic methods, including molecular-based diagnostic methods, that can be used to objectively identify the presence of and/or classify the disease in a patient, define pathophysiologic aspects of rheumatoid arthritis, clinical activity, response to therapy, including response to treatment with various RA therapeutic agents, prognosis, and/or risk of developing rheumatoid arthritis. In addition, it would be advantageous to have molecular-based diagnostic markers associated with various clinical and/or pathophysiological and/or other biological indicators of disease. Thus, there is a continuing need to identify new molecular biomarkers associated with rheumatoid arthritis as well as other autoimmune disorders. Such associations would greatly benefit the identification of the presence of rheumatoid arthritis in patients or the determination of susceptibility to develop the disease. Such associations would also benefit the identification of pathophysiologic aspects of RA, clinical activity, response to therapy, or prognosis. In addition, statistically and biologically significant and reproducible information regarding such associations could be utilized as an integral component in efforts to identify specific subsets of patients who would be expected to significantly benefit from treatment with a particular therapeutic agent, for example where the therapeutic agent is or has been shown in clinical studies to be of therapeutic benefit in such specific RA patient subpopulation.
The invention described herein meets the above-described needs and provides other benefits.
All references cited herein, including patent applications and publications, are incorporated by reference in their entirety for any purpose.